Polycyclic Limonoids as Potential Nrf2 Inducers from Trichilia connaroides

An investigation of Trichilia connaroides uncovered connarolides A-D (1-4, respectively), four limonoids with exceptional multiring systems. Compound 1 showcased a unique 5/8/6/6-fused ring system distinguished by a bicyclo[5.2.1^2,4]decane A/B ring framework. Compound 2 featured a 5/8/6/5/6 scaffold incorporating a triply fused furan ring, and a long-conjugated system resulted from 3-deoxygenation. X-ray crystallography established the rare 6/3/6/6/6 ring system of 3. Moreover, 4 was identified as an antioxidant, conferring cytoprotective activity through Nrf2 activation.